Composition which can be foamed from a pressurized container for producing insulating foams

ABSTRACT

The invention relates to a composition which can be foamed from pressurized containers. Said composition is based on an aqueous plastic dispersion containing an aqueous dispersion of at least one film-forming plastic material consisting of 30% to 80% by weight of a film-forming plastic material, a propellant gas amounting between 3% to 25% by weight in relation to the entire composition and one or more ionic foam stabilizers amounting between 0.3 and 6% by weight in relation to the entire composition. The foamed compositions can he used as scaling, damping and insulating materials.

[0001] The invention relates to a composition that can be foamed frompressurized containers to produce stable insulating foams on the basisof an aqueous plastic dispersion. The composition is in particularsuited to produce insulating foams for use in the building trade.

[0002] The composition according to the invention serves to produceinsulating foams that are primarily used for heat and moistureinsulating applications involving the foam-filling of hollow spaces.Main fields of application are in the building trade but also technicalproducts involving hollow spaces to be filled in order to preventcondensation water from accumulating. Furthermore, such compositions canbe employed for producing seals, e.g. sealing strips.

[0003] Especially in the building sector polyurethane foams arefrequently used that are characterized by a prepolymer composition beingreleased from pressurized containers, for example aerosol containers,with the help of propellants and produced and applied locally and havinga weight per unit of volume ranging between 10 and 100 g/l. Theso-called 1-component foams have moisture-hardening qualities, i.e. theyconsist of a component, namely isocyanate groups, that reacts with theair humidity. 2-component foams contain reactants in the form of asecond component so that the hardening process producing the foam doesno longer or not solely depend on the presence of atmospheric humidity.In this case as well the reactive first component contains isocyanategroups that react with hydroxyl or amine groups present in the secondcomponent.

[0004] Apart from being particularly suitable to yield stable foams theisocyanate groups-containing prepolymers used to produce the customarypolyurethane foams have a decisive disadvantage, i.e. the toxicity ofthe isocyanate containing components. This necessitates specialprecautionary measures to be taken when filling in, processing anddisposing of remaining substances. On the other hand, the PU foamsproduced have good insulating properties, are non-toxic, durable and canbe easily processed and applied.

[0005] Compositions containing polyurethane prepolymers react intenselywith water. For that reason, systems containing such prepolymers cannotbe produced on a water basis. Other liquid components, solvents and/orliquid additives are therefore indispensable as carriers for thefoam-producing components. With respect to the selection of such carriercomponents choices are greatly limited due to the high reactivity of theisocyanate groups. From this point of view it would be desirable to haveavailable foam-producing polymers that could be foamed based on anaqueous dispersion.

[0006] Formulations of film-forming polymers together with propellantgas in a pressurized package for the production of foam pads are knownfrom U.S. Pat. No. 3,912,666. To the formulation disclosed there anon-ionic foam stabilizer is added. The foam has been described as beingnon-adhesive which is consistent with the intended application purposefor cleaning uses.

[0007] In U.S. Pat. No. 4,036,673 a method has been described for theproduction of an adhesive foam with the help of propellant gases from anaqueous dispersion with said foam collapsing after it has formed.

[0008] Furthermore, there are several plastic dispersions on the marketthat are formulated together with propellant gas in a pressurizedpackage and yield a foam that is stable for a short time after foaminghas taken place. This product is intended for the “mending of puncturesin tires”; within the tire the foam distributes over the wall, collapsesto form a film thus sealing punctured spots. Such a formulation has, forexample, been described in U.S. Pat. No. 4,501,825.

[0009] The mechanism of film-forming has been described in literature indetail, cf. “Water-Born-Coatings”, K. Dören et al, Hansa Publishers,München 1994. It is known, moreover, to control the film-forming processby additives such as associative thickeners, film-forming aids, fillersand the like, particularly with respect to optimizing the properties,for example with products of the paint industry, cf. “WässrigePolymerdispersionen, Syntheseeigenschaften-Anwendung”, D. Distler,Wiley-VCH, 1999. The production of foam and the theory of foamstabilization, in particular the production of aqueous foams, have alsobeen covered in sufficient detail in literature, cf. “Handbook ofAerosoltechnology”, p. 358 et seq., “Aqueous Aerosol Films”, P. A.Sanders, Krieger Publishing, Florida 1979.

[0010] Latex foams have occasionally been described for applicationswith pressurized containers. WO-A-98/12 248 describes foamablecompositions for application via pressurized containers in the form ofstable foams that consist of an aqueous emulsion of a film-formingpolymer, a liquid propellant and a solid, lilophilic and non-ionicsurfactant having an HLB of roughly between 3 and 8 and, if necessary,of other additives. WO-A-98/12247 describes a foamable composition forapplication via pressurized containers that contain an aqueous emulsionof a film-forming polymer, a liquid propellant, a solid, wax-like foamstabilizer and a liquid lilophilic surfactant.

[0011] It has been shown that although the foamable compositionsdescribed in the latter two publications immediately after applicationyield a stable foam, this foam, however, collapses over time and on along-term basis does not satisfy the requirements a good insulating foammust meet. Although the foam's pronounced tendency towards shrinkage maybe alleviated by a well-aimed selection of non-ionic surfactants as foamstabilizers, this tendency cannot be eliminated entirely. What is more,the presence of non-ionic surfactants contributes towards instability ofthe produced foams under the influence of moisture, for example whenhigh air humidity conditions prevail.

[0012] Nevertheless, there is demand for a fine-celled, elastic,non-shrinking foam that can be produced by means of a customarypropellant mixture from an aqueous dispersion of a film-forming plasticmaterial. It would be particularly desirable to have such a polyurethanefoam.

[0013] This objective is achieved with the help of a composition thatcontains an aqueous dispersion of at least one film-forming plasticmaterial consisting of 30% to 80% by weight of a film-forming plasticmaterial, a propellant gas amounting to between 3% and 25% by weight inrelation to the entire composition and one or more ionic foamstabilizers amounting to between 0.3 and 6% by weight in relation to theentire composition.

[0014] From the compositions known from the state-of-the-art thecomposition according to the invention relating to the production offoams out of pressurized containers differs in that primarily oneanionic foam stabilizer amounting to between 0.3% and 6% by weight ispresent. A fine-celled, elastic and largely dimensionally stable foam isobtained that behaves mainly inertly under the influence of moisture.

[0015] Aside from their foam stabilizing effect the anionic foamstabilizers used according to the invention have another function thatis they integrate the propellant gases into the aqueous phase. Theformation of an oil-in-water emulsion serves as a model, i.e. thelow-molecular-weight propellant gases are emulsified into the aqueousmedium. It is assumed that for the formation of emulsified propellantgases in the aqueous phase also emulsified propellant gas ‘pellets’ arepresent apart from the dispersed polymer particles.

[0016] The main function of the stabilizers is to ensure the foam'sstability during the film-forming process and during drying. Generallysuitable are anionic, water-soluble foam stabilizers, resp. surfactantsthat after propellant gas driven foaming has taken place form Langmuirfilms at the interface between the constantly aqueous phase and thedispersed gas phase. Surprisingly, the stabilizing effect of ionicsurfactants is significantly superior to that of non-ionic surfactants,particularly as far as foam yield and long-term stabilization areconcerned. Of the ionic surfactants the anionic surfactants arepreferred over the betaines and cationic ones.

[0017] The aqueous plastic dispersions generally used contain 30 to 80%by weight of one or more film-forming plastics, preferably 35 to 70% andin particular 40 to 60%, in relation to the weight of the dispersion. Ingeneral, suitable film-forming plastic materials are those that have aminimum film-forming temperature of less than 100° C., in particularthose having a minimum film-forming temperature of less than 50° C.Suitable film-forming plastic materials that can be used as latex are,alone or in mixed state, those based on acrylic acid, lower alkylacrylates, styrene, vinyl acetate and the like. Polymers on ethylenebasis can be used as well as styrene acrylic copolymers, styrenebutadiene copolymers or vinyl acetate ethylene copolymers. Especiallypreferred is the use of polyurethane latices, alone or in combinationwith the above mentioned latices. The aqueous plastic dispersions put touse are those that are commercially available. In principle, customarylatices, especially those for the production of linings, are suitablefor use in the compositions according to the invention. A list ofexamples can be found in U.S. Pat. No. 4,381,066.

[0018] To produce formulations resistant to frost the use of non-ionicpolyurethane dispersions may prove to be expedient. Such polyurethanedispersions contain hydrophilic polyether chains built into the polymer,cf. Dieterich D., Aqueous Emulsions, Dispersions and Solutions ofPolyurethanes, Synthesis and Properties, Prog. Org. Coat. 9 (1981)281-340. Such polyurethane dispersions can be used alone and togetherwith foam stabilizers of ionic nature, possibly also with non-ionic foamstabilizers.

[0019] With respect to the polyurethane latices mentioned earlier it isto be noted that these due to the hydrophilic and hydrophobic componentsexisting in their molecules form extraordinarily stable dispersions thatpractically do not need any additional stabilizers. This is true bothfor polyurethanes on the basis of aromatic and aliphaticpolyisocyanates, irrespective of whether they have been cross-linkedwith polyetherols or polyesterols. Furthermore, polyurethane latices incombination with the anionic foam stabilizers used according to theinvention are capable of integrating propellant gases such asliquefiable hydrocarbons, dimethyl ether or liquefiable fluorocarbons ofsufficient quantity into the aqueous dispersions and cause them to befinely distributed so that a remarkably fine-celled, elastic and stilldimensionally stable foam is produced. Due to the fact that aqueouspolyurethane dispersions have pronounced self-stabilizingcharacteristics there is, as a rule, no need to add the customaryemulsifiers.

[0020] In the compositions according to the invention mixtures ofvarious latices can be advantageously used. This, in particular, alsoapplies to those latices that differ with respect to their minimumfilm-forming temperatures since it was found that at a minimumfilm-forming temperature below room temperature very fine-celled, softelastic foams are obtained, whereas if the minimum film-formingtemperature is above room temperature fine-celled foams are obtainedthat after drying over night appeared to be rather brittle. Thecombination of a latex having a film-forming temperature of 20° C. orless, particularly=0° C., with a latex having a minimum film-formingtemperature above 20° C. results in the properties to be balanced out toa great extent so that a fine-celled, elastic, dimensionally stable foamis obtained that can be easily processed. As a rule, such mixturesshould contain the two components with their weight relationship rangingbetween 30/70 and 70/30.

[0021] The compositions according to the invention may contain additivesof customary nature such as, for example, flame retardants, thickeners,biocides, fungicides, algicides, antifreeze agents, anti-corrosionagents, emulsifiers, fillers, film-forming aids and the like. Thisapplies to such additives as they are customarily employed in theproduction of insulating foams, aqueous dispersions and compositionsthat are intended to be applied from pressurized containers.

[0022] As flame retardants those agents can be used that are customarilyemployed in insulating foams provided that such retardants are capableof being admixed to the aqueous dispersion. Preferred flame retardantsare dispersions of flame retarding agents on polymer basis such as, forexample, PVC dispersions, polyvinylidene chloride dispersions orpolychloroprene latices as are available on the market.

[0023] As auxiliary agent for the thickening of the latices suchthickening agents can be used as are, for example, employed for aqueousvarnishes. Thickening may, in particular, become necessary if it isenvisaged to use solid substances such as customary halogen-free flameretardants (ammonium polyphosphate, aluminum hydroxide, boric salts) orother functional additives as fungicides, insecticides, algicides andthe like. Suitable thickening agents are, for example, cellulosederivates such as Methocel^(R) 228, Methocel^(R) A, Methocel^(R) 311(DOW Chemical), acrylate thickeners for aqueous systems e.g. A P1/1(Münzing-Chemie) and Mirox AM (Stockhausen), polyurethane thickeners foraqueous systems e.g. Tafigel^(R) PUR 40, Tafigel^(R) PUR 55 (MünzingChemie) as well as inorganic thickeners as bentonite, hectorite,montmorillonite, silicic acids (Aerosil^(R) 200 from Degussa).

[0024] Especially thickeners based on short-chained polyurethanes, suchas the Tafigel types, promote the formation of firm foams and areconducive to the formation of a homogenous cell structure when rawmaterials of low viscosity are used. Good stability is particularlydesirable if vertical joints have to be foamed.

[0025] The combination of dispersions of film-forming polymers onnon-polyurethane basis with thickeners on polyurethane basis yieldscompositions that in terms of quality are comparable to the polyurethanedispersions for the production of foam. As a result of the formation ofstable structures in aqueous systems it is even possible to dispensewith the addition of customary emulsifiers entirely or in part ifpolyurethane thickening agents are employed.

[0026] For special applications customary biocides can be added to thefoams, for example to ward off or take precautionary measures againstinsect damage, algae growth or fungal attack.

[0027] As it has to be expected that the compositions according to theinvention have to be stored under unfavorable conditions for prolongedperiods of time before they are applied it may be useful and practicalto add customary antifreeze agents and anti-corrosion agents. Examplesof such agents are ethylene glycol, propylene glycol and diethyleneglycol. Suitable anti-corrosion agents are alkanolamines.

[0028] Further additives are film-forming auxiliary agents capable ofreducing the minimum film-forming temperature and such additives can beselected on the basis of the hydrophobic or hydrophilic qualities of thefilm-forming polymers according to Diestler, for example Texanol^(R),propylene glycol, Dowanol^(R)DPM.

[0029] Due to the fact that the plastic dispersions are aqueous systemshaving a high water content it may be necessary to add auxiliary agentsthat ensure the solubility and dispersibility of the additives andpropellant gases as well as the formation of a homogenous and stablephase. The formation of an oil-in-water emulsion serves as a model, i.e.the low-molecular-weight propellants and the additives used areemulsified into the aqueous medium.

[0030] In the event polyurethane dispersions are employed the use ofemulsifiers can be dispensed with to a great extent. Otherwise, suchemulsifiers can be used as they are employed in the production ofplastic dispersions in emulsion polymerization, for pharmaceuticalapplications producing gels and creams and for the solubilization ofcolorants and dyestuff. Emulsifiers from the surfactants series areespecially suited. Examples here are ethoxilated fatty alcohols,ethoxilated alkyl phenols, ethoxilated fatty acids, alkyl sulfates,alkyl ether sulfates, cocobetaines, alkylamidopropyl sulfobetaines,alkyl dimethyl benzyl ammonium bromides, sorbitan esters as sorbitanmonopalmitate, -monosterarate and -monooleate, ethoxilated castor oil,ethoxilated hydrated castor oil and the like. Further non-ionicemulsifiers and protective colloids that may also be used in combinationwith ionic emulsifiers are, for example, polyvinyl alcohols, polyvinylpyrrolidon as well as amphiphilic block copolymers of ethylene oxide andpropylene oxide, such as for example Pluronics^(R) from BASF orSynperonics^(R) from ICI Surfactants.

[0031] The anionic foam stabilizers as a rule are soaps and surfactants.These are present in an amount of between 0.3 and 6% by weight inrelation to the entire composition, preferable in an amount rangingbetween 0.5 and 4% and in particular between approximately 1 and 3%.Preferably acceptable are soaps such as ammonium, sodium and potassiumsoaps, especially ammonium or sodium stearate, -laurate, -myristate and-palmitate.

[0032] Furthermore, suitable are also derivates of fatty acids of thegeneral formula RCO—N (CH₃)CH₂COONa, where RCO denotes a lauric,myristic, palmitic, stearic or oleic acid residue. These fatty acidderivates are generally known as sarcosinates.

[0033] Furthermore, fatty alkyl ether carboxylates of the generalformula R—(OCH₂CH₂)_(n)—OCH₂COONa can be used, where R denotes a fattyalkyl residue. Suitable are α-sulfo fatty acid methyl ester, fatty alkylsulfates, fatty alkyl ether sulfates, alkyl phosphates and alkyl etherphosphates, alkyl benzene sulfonates, olefine sulfonates, alkanesulfonates as well as sulfo succinate or sulfo succinate of fatty acidalkanolamides.

[0034] Of the α-sulfo fatty acid esters those of formulaRCH(SO₃H)(COOCH₃), and, respectively, their salts, are preferred, whereR denotes a fatty alkyl residue. Especially preferred of the fatty alkylsulfates is Stokal^(R) SAF, an ether sulfate of C₁₂-C₁₅ fatty alcoholethoxylates with 2 to 3 ethylene oxide units, approximately of formulaC₁₂H₂₅(OCH₂CH₂)₂₋₃OSO₃H, sodium salt.

[0035] The alkyl phosphates and alkyl ether phosphates are commerciallyavailable substances which applies also to the alkyl benzene sulfonatesof which dodecyl benzene sulfonate is given preference. Of the olefinesulfonates the C₁₄- and C₁₆ homologs are preferred, of the alkanesulfonates those having 13 to 18 carbon atoms. It applies, inparticular, that of the fatty acid derivates especially those having 10to 20 carbon atoms are considered suitable.

[0036] Especially preferred anionic foam stabilizers are soaps and fattyalcohol sulfates (for example products of the company of Stockhausen,Krefeld, Germany) that are available on the market under the name ofStokal^(R)STA and Sultafon^(R)SAF. Using a combination of ammoniumstearate and fatty alcohol sulfate a fine-tuning of the foam structurecan be achieved.

[0037] As cationic foam stabilizers customary benzalkonium salts, alkyltrimethyl ammonium salts as well as fat alkonium salts may, for example,be used. As salts, particularly the chlorides and methosulfates arepreferred. Examples are an alkyl dimethyl benzyl ammonium chloride ofthe tradename Empigen BAC 50, alkyl trimethyl ammonium methosulfatehaving the tradename of Empigen CM (both from Albright and Wilson), aC12-C14 alkyl benzyl dimethyl ammonium chloride known by the tradenameof Servamine KAC 422 D (from Condea) as well as a stearalkonium chlorideof tradename Ninox 4002 (from Stepan).

[0038] Preferred cationic foam stabilizers are, furthermore,lipophilically modified quaternized proteins, as are offered, forexample, by The Mcintyre Group under the name of Macropro. These arehydrolized protein units that are for instance derived from hydrolizedcollagen, keratin, wheat protein, soja protein or hydrolized silk ormilk and have been modified by means of natural lipide residue via aquarternary ammonium group.

[0039] Also suitable are metaines, i.e. surfactants of amphotericcharacter (zwitterions). Of suitable type are in this case fatty acid,amido alkyl betaines, for example coconut fatty acid amido propyl betainund coconut fatty acid amido propyl sulfobetain, and also fatty acidamphoacetates, e.g. lauroamphoacetate. Tradename products would beAmpholit JB 130 K made by Kondea, Ammonyl 675 SB from Sepik and EmpigenCDL 60/P from Albright and Wilson.

[0040] The propellant gases used in the composition according to theinvention are those that are customarily employed for the generation offoams in pressurized containers. Suitable are, in particular,liquefiable propellant gases such as propane, n-butane, isobutane,dimethyl ether, 1,1,1,2-tetrafluoromethane (R134a) and1,2-difluoromethane (R152a), solely or in a mixture. Particularlypreferred is a mixture of propane, isobutane and dimethyl ether. Assupplementary and supporting media further propellant gases such as CO₂or N₂O may be admixed. The propellant gas content of the entirecomposition amounts to between 3 and 25% by weight, preferably up to 20%by weight and in particular up to 12% by weight. For the production ofsealing foams and strings a propellant gas content of between 3 and 5%by weight will be fully sufficient as a rule. For the production ofsealing foams using CO₂ as propellant gas, for the most part or solely,is sufficient and preferred.

[0041] The latex types are selected in view of their film-formingtemperature. A film-forming temperature of below 100° C. is of primeimportance. However, the minimum film-forming temperature can be reducedto the desired range through the use of suitable film-forming auxiliaryagents.

[0042] Especially preferred is the use of polyurethane dispersions aswell as dispersions consisting of polyurethane and another film-formingagent, e.g. polyurethane acrylate combinations. For certain applicationsthe use of hydrophobic film-forming agents may be useful, for examplethose of olefinic basis or having a high olefinic content, e.g. styrenebutadiene copolymers and styrene acrylate copolymers. It has beennoticed that when using high proportions of hydrophilic plastics, e.g.high proportions of vinyl acetate ethylene propolymer, the waterabsorption capability increases considerably resulting in the producedfoam becoming saturated with water when the relative humidity is highcausing it to partially dissolve and soften. This may lead to aninternal collapse of the metastable foam and loss of the desirablethermal and sound insulating properties.

[0043] An overview of the latices than can be employed is given inTable 1. With regard to the polyurethane dispersions it is to be notedthat for the production of UV stable foams the use of polyurethane basedon aliphatic polyisocyanates is preferred.

[0044] Furthermore, the invention relates to pressurized containersfilled with the above described composition and intended to applyinsulating foams. These are customary aerosol or pressurized containersas used worldwide for various purposes, inter alia for the production of1-component polyurethane insulating foams on the basis of isocyanateprepolymers. To improve the applicability of the compositions stored insuch pressurized containers for longer periods of time it may be usefulto integrate into the filled pressurized container an application aid inthe form of a metal rod or steel ball facilitating the stirring orshaking of a dispersion that has settled down. TABLE 1 Latex % SolidsMFBT ° C. pH Viscosity mPas Manufacturer Remark Styrene butadienecopolymerisates Lipaton SB 4520 50 0 8.5 200 Polymer-Latex, Marl LipatonSB 5521 50 0 8.5 100 Polymer-Latex, Marl Lipaton SB 5811 47 3 8 25Polymer-Latex, Marl Lipaton SB 5850 46 3 8 20 Polymer-Latex, Marl DL 95550 18 7 200 DOW DL 980 50 0 5 250 DOW Styrene acrylate copolymerisateLipalon X 3820 50 4 7.5 160 Polymer-Latex, Marl Lucidene 375 45 85 8.5350 Morton International, Bremen Vinyl acetate ethylene copolymerVinnapas LL 7200 72 2300 Air Products. Burghausen (Airflex 720)Polyurethane dispersion U 500 40 0 7.4 400 Alberdingk Boley, KrefeldPUR/Polyether U 600 A 40 0 8 300 Alberdingk Boley, Krefeld U 210 61 0 81000 Alberdingk Boley, Krefeld PUR/Polyether U 300 40 0 — — AlberdingkBoley, Krefeld PUR/Polyether U 650 40 0 — — Alberdingk Boley, KrefeldPUR/Polyether Impranil DLNW 50 50 — — — Bayer AG PUR/Polyether Acrylatedispersion AC 548 50 13 8 4500 Alberdingk Boley, Krefeld AC 2535 50 207.5 3000 Alberdingk Boley, Krefeld AC 31 50 40 7.5 1000 AlberdingkBoley, Krefeld AC 2529 43 50 7 4500 Alberdingk Boley, Krefeld AC 2509 5080 7.5 500 Alberdingk Boley, Krefeld Acrylic-methacrylic esterdispersion AC 548 50 13 8 4500 Alberdingk Boley, Krefeld

[0045] The compositions according to the invention are formulated asfollows. Foam stabilizers and, if thought necessary, emulsifiers arethoroughly stirred into and thus added to the prepared latex mixture.When using water-insoluble components these must be initially dissolvedin organic solvents and then slowly admixed with the latex. The factthat this process enables higher concentrations to be admixed than couldbe expected from its solubility in water is presumably due to the micellformation capability and/or the incorporation of surfactants into thelamellar layers of the dispersed polymer particles at the polymer-waterinterface.

[0046] Low-molecular-weight alcohols such as ethanol, propanol,isopropyl alcohol, butanol, isobutanol, tert-butanol, ethylene glycol,isobutyl glycol, diethylene glycol, 1-methoxy-2-propanol,1-ethoxy-2-propanol and the like have turned out to be suitable organicsolvents for the aqueous dispersions according to the invention.

[0047] If solutions are needed these are to be made in the presence ofheat. Some systems, for example hexadecanoic acid, 40%, in isopropanolcan only be worked for a few hours after they have cooled down since apronounced micell build-up and the formation of liquid-crystallinestructures will occur. Such structures can then be eliminated by heatingand stirring.

[0048] It is obvious that the anionic surfactants can also be producedby a neutralization of the relevant acids in a basified aqueousdispersion or in an aqueous dispersion of a film-forming agent havingbasic functions.

[0049] After the addition of surfactants and, if thought necessary,emulsifiers further additives are incorporated and, when the pressurizedcontainer has been filled and closed off, the propellant gas is applied.

[0050] The invention is explained by way of the following examples.

EXAMPLES 1 to 7

[0051] Pressurized containers were filled with compositions, as perTable 2, according to the invention, closed off and tested after somedays of equilibration.

[0052] All compositions yielded foams having a weight per unit of volumeof approximately 100 g/cm³. Best results were achieved with compositionsbased on dispersions of polyurethanes or mixtures containingpolyurethanes. In that case dimensionally stable, fine-celled, elasticfoams were obtained that showed good to very good adhesive power.

[0053] From Example 5 it is evident that when using a non-ionic foamstabilizer (Brij 52) the foam lacks the durability that is necessary.After 24 hours the foam had collapsed; the composition is not suitablefor the foaming of joints.

[0054] As a rule, dispersions not containing polyurethane yielded poorerresults in that the foam either exhibited shrinkage (Example 3) or wasbrittle or crumbly (Example 4). However, the tendency towards crumblingcould be set off by admixing polyurethane dispersion (Example 7).

[0055] All foams showed good adhesive power with respect to wood andother materials. This is particularly important for use in the buildingtrade where insulating foams are routinely employed for the foaming ofdoor and window casings.

[0056] When adjusting the compositions according to the invention tohave a propellant gas content of between 3 and 5% by weight they arecapable of being foamed in the form of sealing strings as are forinstance applied in building joints but also in refrigerators. TABLE 2Substance 1 2 3 4 5 6 7 U 210  82  88  85 U 500  82 U 600 A  42 AG 2529 82  40 DL 955  82  2.5 Stokal STA Sultafon SAF  9  9  9  9  9  2.5 Brij52 solution  3 ethox. nonyl phenol  3 Propane  2  2  2  2  2  4Isobutane  3  3  3  3  3  3  2 Dimethyl ether  4  4  4  4  4  3  4 Total100 100 100 100 100 100 100 Cell pattern in 1 cm of fine- fine-fine-celled, fine-celled collapsed compact, elastic joint celled celledsevere fine-celled shrinkage Elasticity highly highly soft, non-elasticbrittle-crumbly highly elastic highly elastic elastic elastic Adhesivepower very very good good very good very good good good

1. A composition on the basis of an aqueous plastic dispersion that canbe foamed from pressurized containers and contains an aqueous dispersionof at least one film-forming plastic material consisting of 30% to 80%by weight of a film-forming plastic material, a propellant gas amountingto between 3% and 25% by weight in relation to the entire compositionand one or more ionic foam stabilizers amounting to between 0.3 and 6%by weight in relation to the entire composition.
 2. The compositionaccording to claim 1, characterized in that the aqueous plasticdispersion contains 40 to 60% by weight of film-forming plasticmaterial.
 3. The composition according to claims 1 or 2, characterizedin that the minimum film-forming temperature is below 100° C.
 4. Thecomposition according to one of the above claims, characterized in thatthe minimum film-forming temperature is below 50° C.
 5. The compositionaccording to one of the above claims, characterized in that the aqueousdispersion contains a polyurethane, a polyacrylate, a styrene butadienecopolymer, a vinyl acetate ethylene copolymer, an acrylic-methacrylicacid copolymer or a mixture of same.
 6. The composition according toclaim 5, characterized in that the aqueous dispersion contains a mixtureof a polyurethane and another plastic material.
 7. The compositionaccording to claims 5 or 6, characterized in that two film-formingplastic materials are provided in the mixture at a mixing ratio ofbetween 30/70 and 70/30 by weight, of which one has a minimumfilm-forming temperature of 20° C. or less and the other has a minimumfilm-forming temperature of more than 20° C.
 8. The compositionaccording to one of the above claims, characterized by customaryadditives in the form of flame retarding agents, thickeners, biocides,fungicides, algicides, antifreezing agents, fillers, anti-corrosionagents and/or emulsifiers of a total amount of up to 50% by weight inrelation to the entire composition.
 9. The composition according to oneof the above claims, characterized in that the foam stabilizer(s) are ofanionic, cationic or amphoteric nature.
 10. The composition according toclaim 9, characterized in that the foam stabilizer(s) are selected fromcarboxylates, derivates of fatty acids, fatty alkyl ether carboxylates,alpha-sulfo fatty acid methly ester, fatty alkyl sulfates, fatty alkylether suffates, alkyl phosphates, alkyl ether phosphates, alkyl benzenesulfonates, alkane sulfonates, olefine sulfonates, sulfo succinateand/or sulfo succinate of fatty acid alkanolamides.
 11. The compositionaccording to claim 9, characterized in that the foam stabilizer(s) areselected from lipophilic, modified, quarternary proteins, benzalkoniumsalts, trimethyl alkyl ammonium salts and/or fatty alkonium salts. 12.The composition according to claim 9, characterized in that the foamstabilizer(s) are betaines.
 13. The composition according to one of theabove claims, characterized in that the foam stabilizers are present inan amount of between 1.0 and 4.0% by weight in relation to the entirecomposition.
 14. The composition according to one of the above claims,characterized in that the propellant gas is a mixture of liquefiablepropellant gases.
 15. The composition according to claim 11,characterized in that the liquefiable propellant gases are propane,butane, isobutane and/or dimethyl ether.
 16. The composition accordingto one of the above claims, characterized in that said compositioncontains CO₂ and/or N₂O as propellant gas.
 17. Use of the compositionaccording to one of the above claims for the production of sealing andinsulating substances, in particular for thermal insulation purposes.18. Use according to claim 17 for the production of insulating strips.19. A pressurized container containing a mixture according to one of theclaims 1 to
 16. 20. The pressurized container according to claim 19,characterized in that it additionally contains a steel ball.